This animation shows several zoomed-in views of the rock dubbed "Humphrey" following its successful grinding with the Mars Exploration Rover Spirit's rock abrasion tool. These microscopic images were taken at varying heights to bring the rock surface into focus. By combining these images, scientists can also create three-dimensional models. The images were acquired on the 60th martian day, or sol, of the rover's mission by its microscopic imager. The observed area is 3 centimeters (1.2 inches) across.